Method of reconditioning cutting tools



Patented Apr. 28, 1931 estates UNITED STATES PATENT, OFFICE.

MAX MENDEL TURNER, F IiONDON, ENGLAND V METHOD OF BECONDITIONING CUTTING TOOLS NoDmwing. Application filed August 9; 1929, Serial No. 384,811, and in Great Britain April 3,. 1929.

- This invention relates to the renovation or re-cond-itioning of cutting tools such as files, angers, saws, broaches, screw dies, matrices, and similar tools for cutting wood and 6 metal, all. hereinafter and in the appended claims included in the term cutting tool which term, however, is not intended to in.- chide sharp edged tools such as plane knives and chisels.

10 According to my invention the worn surfaces of the cleaned cutting tools are coated with an acid resisting material prior to the subjection of. the tool to the action of a suit able, acid.

. The backing of the teeth may also be part- 1y or wholly covered with said acid resisting material prior to the/subjection of. the tool to the action of acid. 7

Thetool may be subjected more than once 29 tothe. action of acid and also; if desired to the action of an alkalifor example a boilingsolution: of caustic potash.

I propose to describe, by way of example,

a method of renovating cutting tools which- 5 I have found to be satisfactory, but wish it to'be-understood'that. I do not limit the scope of my invention to the particularsteps, nor to the particular substances or proportionsthereof, set forth.

-30 In accordance with said method, the tooling to the humidity of the atmosphere but usually being from about two to five per cent. The, tool is maintained in this bathonly a short time (theti-me may be merely sufficient so'that the tool is heated to the temperature oftthe bath); and is then speedily dried.

Thetool is then brushed (preferably with I a wire brush) and carefully examined to make sure that it is entirely free from impurity or foreign matter. V

The shining parts or blunt cutting edges of the teeth of the file or tool are then coated With an isolating varnish or other acid resist, ing material which is applied in the direction opposite to the cutting direction of the teeth (so that part at leastof the backing'portions of each of the teeth is also coated). by means. of a rubber cylinder, gelatine, or other suita-- ble pliable instrument or material. A suita blevarnish may conveniently be prepared by making a saturated: solution of Barbados: tar

in. oil of turpentine and adding if desired oil varnish. thereto according to the temperature.

When the isolating varnish is quite dry the tool is subjected to the action of a jet of water under highpressure whereby any air bubbles adhering to it are removed.

The tool is then suspended in an acid. bath consisting of ninety-five percent of water, four per cent of nitric acid at 40, and one per cent of sulphuric acid at 66 whereby the metal parts not protected by the. varnish is etched away. The tool and/or the bath may be shaken to remove gas bubbles from the metal and the period of immersionv will vary according to the size of the tool and/or its degree of bluntness. I. have found that about two hours is sufficient for small files.

The file or tool is then again treated forten minutes with a boiling solution of caustic potash to ensure its being quite clean and afterwards washed in cold Water and treated for two or three minutes in a bath of sulphuric acid (about five per cent at 66).

The tool is then washed and then subjected to the action of a mechanically'operated circular brush whereby all trace of the isolating varnish, carbon, and bosses, knobs, or the like, which may have been formed, will be re.- moved.

After further washing with water the tool is immersed in the nitric and sulphuric acids bath, for a time depending upon its size, structure, hardness and the amount of wear it has had, the time usually varying from one to ten hours. (I have found that a hundred litres of the acid solution will treat about fifty-one square metres of average metal surface.)

The file or tool is then brushed with the circular brush under a ct of water, and finally is immersed again in the second bath and then dried and oiled or varnished.

Claims 1. An improved method of reconditioning cutting tools which consists in cleaning the tool, coating the worn surfaces of the cleaned tool with an acid resisting material, subjecting the tool to the action of acid, treating the tool with a boiling solution of caustic potash, subjecting it again to the action of acid, and finally again cleaning it.

2. An improved method of re-conditioning cutting tools which consists in cleaning the tool, coating the worn surfaces and the backing portions of the teeth of the tool with an acid resisting material, subjecting the tool to the action of acid, treating the tool with a boiling solution of caustic potash, subjecting it again to the action of acid, and finally again cleaning it.

3. An improved method of re-conditioning cutting tools which consists in cleaning them by immersion in a boiling solution of caustic potash. coating the worn surfaces of the cleaned tool with an acid resisting material,

subjecting the tool to the action of acid,

again treating the tool with a boiling solution of caustic potash, subjecting it again to the action of the acid, and finally again cleaning it.

4. An improved method of re-conditioning cutting tools according to which the worn surfaces of the cleaned tool are coated with an acid resisting material, and the tool then subjected to the action of a solution of 4% nitric acid at 40, and 1% sulphuric acid at 66, in water.

5. An improved method of re-conditioning cutting tools according to which the worn surfaces of the cleaned tool are coated with a solution of Barbados tar in oil of turpentine, allowing the solution to dry, and subjecting the tool to the action of a solution of 4% nitric acid at 40, and 1% sulphuric acid at 66, in water.

6. An improved method of reconditioning cutting tools which consists in cleaning the tool, coating the worn surfaces of the cleaned tool with an acid resisting material, subjecting the tool to the action of a solution of 4% nitric acid at 40, and 1% sulphuric acid at 66, in water, treating the tool with a boiling solution of caustic potash, subjecting it again to the action of acid, and finally again cleanin it.

3. An improved method of reconditioning cutting tools, which consists in cleaning the tool, coating the worn surfaces of the cleaned tool with a solution of Barbados tar in oil of turpentine, allowing this solution to dry, subjecting the tool to the action of a solution of 4% nitric acid at 40, and 1% sulphuric acid at 66, in water, treating the tool with a boiling solution of caustic potash, subjecting it again to the action of acid, and finally again cleaning it.

8. An improved method of reconditioning cutting tools which consists in coating the worn surfaces of the tool with an acid resisting material, subjecting the tool to the action of acid, treating the tool with a boiling solution of caustic potash, again subjecting it to the action of acid, then cleaning it to remove all traces of said material, bosses,

and carbon, then again treating it with acid,

and finally again cleaning it. l s

9. An improved method of re-conditioning cutting tools which consists in coating the worn surfaces of the tool-with a solutionof Barbados tar inoil of turpentine, allowing the solution to dry, subjecting the tool to the action of acid, treating the tool with a boiling solution of caustic potash, again subject ing it to the action of acid, then cleaning it to remove all traces of tar, bosses, and'carbon, then again treating it with acid, and finally again cleaning it. I

10. An improved method of re-condition ing cutting tools which consists in coating the worn surfaces of the tool with a solution of Barbardos tar in oil of turpentine, allowing this solution to dry, subjecting the tool to the action of a solution comprising 4% nitric acid at 40, and 1% sulphuric acid at 66, in water, treating the tool with a boil ing solution of caustic potash, again subjecting it to the action of acid, then cleaning it'to remove all traces of tar, bosses, and carbon, again treating it with acid, and finally cleaning it; i

11. An improved method of re-conditioning cutting tools which consists in coating the worn surfaces of the tool with an acid resisting material, subjecting the tool to the action of an acid solution comprising 4% nitric acid at 40, and 1% sulphuric acid at 66 in water, treating the tool with a boiling solution of caustic potash, subjecting the tool to the action of an acid solution comprising 5% sulphuric acid at 66 in water,

prising a solution of Barbados tar in oil of turpentine to which is added oil varnish, allowing'the varnish to dry, subjecting the ids iio 

